Attribute Values

XML attributes are written as strings. Generated inflaters turn those strings into the Dart values required by Flutter constructors: numbers, colors, insets, durations, enums, and other common UI types.

Use this page when you know the Dart type of an attribute and need the exact XML format to write.

Some sections list accepted strings, but those strings are parser keywords, literal formats, or Flutter constant names. Dart enum attributes are covered separately in Enum Values.

Alignment

The parser accepts these Flutter Alignment constant names for non-directional layout positions:

topLeft, topCenter, topRight,
centerLeft, center, centerRight,
bottomLeft, bottomCenter, bottomRight

<Align alignment="center">
    <Text data="Centered" />
</Align>

AlignmentDirectional

The parser accepts these Flutter AlignmentDirectional constant names when the position should resolve with text direction. start and end replace physical left and right.

topStart, topCenter, topEnd,
centerStart, center, centerEnd,
bottomStart, bottomCenter, bottomEnd

<Scaffold persistentFooterAlignment="centerEnd">
    <Text for="body" data="Page content" />
</Scaffold>

AlignmentGeometry

The parser accepts both physical Alignment constants and directional AlignmentDirectional constants.

<Container alignment="bottomEnd">
    <Text data="Bottom end" />
</Container>

bool

Boolean values are true or false. Matching is case-insensitive.

<Visibility visible="true">
    <Text data="Visible content" />
</Visibility>

BorderRadius and BorderRadiusGeometry

The value is a numeric shorthand that can set every corner, vertical pairs, or each corner individually.

XML value	Result
`8`	All corners use radius `8`.
`8,12`	`BorderRadius.vertical(top: 8, bottom: 12)`.
`1,2,3,4`	`topLeft: 1`, `topRight: 2`, `bottomRight: 3`, `bottomLeft: 4`.

<Container>
    <BoxDecoration for="decoration" borderRadius="8" />
</Container>

<Container>
    <BoxDecoration for="decoration" borderRadius="4,8,12,16" />
</Container>

Color

Colors accept 6-digit RGB or 8-digit ARGB hex. The # and 0x prefixes are optional.

XML value	Meaning
`#0066CC`	Opaque RGB color.
`0066CC`	Same as `#0066CC`.
`0x0066CC`	Same as `#0066CC`.
`#800066CC`	ARGB color with alpha `80`.
`800066CC`	Same as `#800066CC`.
`0x800066CC`	Same as `#800066CC`.

<Container color="#F4F6F8" />
<Container color="0x80FF0000" />
<TextStyle color="@color/primary" />

Curve

The parser accepts these Flutter Curves constant names:

bounceIn, bounceInOut, bounceOut,
decelerate,
ease, easeIn, easeInBack, easeInCirc, easeInCubic, easeInExpo,
easeInOut, easeInOutBack, easeInOutCirc, easeInOutCubic,
easeInOutCubicEmphasized, easeInOutExpo, easeInOutQuad,
easeInOutQuart, easeInOutQuint, easeInOutSine,
easeInQuad, easeInQuart, easeInQuint, easeInSine, easeInToLinear,
easeOut, easeOutBack, easeOutCirc, easeOutCubic, easeOutExpo,
easeOutQuad, easeOutQuart, easeOutQuint, easeOutSine,
elasticIn, elasticInOut, elasticOut,
fastLinearToSlowEaseIn, fastOutSlowIn,
linear, linearToEaseOut, slowMiddle

<MaterialApp themeAnimationCurve="easeInOut">
    <Text for="home" data="Home" />
</MaterialApp>

double

Double values are parsed with double.parse. The value infinity maps to double.infinity.

Because the default config includes *:width and *:height, width and height attributes use this parser even when the reflected Dart type is not enough to infer it.

<SizedBox width="240" height="120" />
<SizedBox width="infinity" />
<TextStyle fontSize="14" height="1.4" />

Duration

Durations are an integer immediately followed by a unit. Do not add spaces between the number and the unit.

Units	Meaning
`ms`, `milli`, `millis`, `milliseconds`	Milliseconds
`s`, `sec`, `secs`, `seconds`	Seconds
`m`, `min`, `mins`, `minutes`	Minutes
`h`, `hr`, `hrs`, `hour`, `hours`	Hours
`d`, `day`, `days`	Days

<MaterialApp themeAnimationDuration="250ms">
    <Text for="home" data="Home" />
</MaterialApp>

<MaterialApp themeAnimationDuration="2s">
    <Text for="home" data="Home" />
</MaterialApp>

EdgeInsets and EdgeInsetsGeometry

Insets accept either one value for every side or four values in left, top, right, bottom order. Two-value shorthand is not part of the default parser.

XML value	Result
`16`	`EdgeInsets.all(16)`.
`8,12,8,12`	`EdgeInsets.fromLTRB(8, 12, 8, 12)`.

<Padding padding="16">
    <Text data="All sides" />
</Padding>

<Padding padding="8,12,8,12">
    <Text data="Left, top, right, bottom" />
</Padding>

Enum Values

Enum attributes use the generic enum parser generated for constructor arguments whose Dart type is an enum. The generated parser calls parseEnum() with that enum's .values, so the XML value must match one of the enum constant names.

<Column mainAxisAlignment="center" crossAxisAlignment="start" />

<TextStyle fontStyle="italic" overflow="ellipsis" />

<ThemeData brightness="dark" materialTapTargetSize="shrinkWrap" />

Here center maps to MainAxisAlignment.center, and start maps to CrossAxisAlignment.start. Likewise, italic maps to FontStyle.italic, and dark maps to Brightness.dark. The accepted values come from the enum type of the constructor argument.

If the generated inflater XSD is registered in your editor, enum attributes show the valid options from that enum in XML completion and validation.

FontWeight

The parser accepts common names, numeric weights, and Flutter-style w### names.

XML values	Result
`thin`, `100`, `w100`	`FontWeight.w100`
`extraLight`, `200`, `w200`	`FontWeight.w200`
`light`, `300`, `w300`	`FontWeight.w300`
`regular`, `normal`, `400`, `w400`	`FontWeight.w400`
`medium`, `500`, `w500`	`FontWeight.w500`
`semiBold`, `600`, `w600`	`FontWeight.w600`
`bold`, `700`, `w700`	`FontWeight.w700`
`extraBold`, `800`, `w800`	`FontWeight.w800`
`black`, `900`, `w900`	`FontWeight.w900`

<TextStyle fontWeight="bold" />

IconData

Icons are looked up by registered icon name. Generated icon names include the icon set prefix, such as Icons.add or CupertinoIcons.cube. The default config also parses any argument named icon or activeIcon as IconData.

<Icon icon="Icons.add" />

InputBorder

The parser accepts these keywords:

none, outline, underline

<TextField>
    <InputDecoration for="decoration" border="outline" />
</TextField>

int

Integer values are parsed with int.parse.

<Text data="Only show two lines" maxLines="2" />

Key

Use the unique keyword when a fresh UniqueKey should be created. Any other value becomes a ValueKey with that string.

XML value	Result
`unique`	`UniqueKey()`
any other value	`ValueKey(value)`

<Container key="settings-panel" />
<Container key="unique" />

List<T>

List parsers split comma-separated values and trim whitespace around each item. A single value becomes a one-item list.

Dart type	XML value	Result
`List<String>`	`alpha,beta,gamma`	`['alpha', 'beta', 'gamma']`
`List<double>`	`1, 2.5, 3`	`[1.0, 2.5, 3.0]`
`List<int>`	`1, 2, 3`	`[1, 2, 3]`

<TextStyle fontFamilyFallback="Inter,Roboto,Arial" />

<LinearGradient stops="0,0.5,1" colors="${gradientColors}" />

Locale

Locales accept a language code alone or a language and country separated by an underscore. The parser lowercases the language code and uppercases the country code.

XML value	Result
`en`	`Locale('en', null)`
`en_US`	`Locale('en', 'US')`

<Text data="Hello" locale="en" />
<Text data="Howdy" locale="en_US" />

Offset

Offsets accept one value for both axes or two values for dx and dy.

XML value	Result
`8`	`Offset(8, 8)`
`8,12`	`Offset(8, 12)`

<PopupMenuButton itemBuilder="${buildMenuItems}" offset="4" />

<PopupMenuButton itemBuilder="${buildMenuItems}" offset="4,12" />

Size

Sizes accept square, width-height, and unbounded forms. A missing side in the x form becomes double.infinity.

XML value	Result
`24`	`Size(24, 24)`
`24x16`	`Size(24, 16)`
`24,16`	`Size(24, 16)`
`24x`	`Size(24, double.infinity)`
`x16`	`Size(double.infinity, 16)`

<SizedBox.fromSize size="24">
    <Text data="Square" />
</SizedBox.fromSize>

<SizedBox.fromSize size="120x40">
    <Text data="Wide" />
</SizedBox.fromSize>

String

Strings are passed through unchanged.

<Text data="Settings" />

TextDecoration

The parser accepts these Flutter TextDecoration constant names:

lineThrough, overline, underline, none

<TextStyle decoration="underline" />

TextInputType

The parser accepts these Flutter TextInputType constant names:

datetime, emailAddress, multiline, name, none, number, phone,
streetAddress, text, url, visiblePassword

<TextField keyboardType="emailAddress" />

VisualDensity

Visual density accepts one value for both axes or two values for horizontal and vertical density.

XML value	Result
`1`	`VisualDensity(horizontal: 1, vertical: 1)`
`1,2`	`VisualDensity(horizontal: 1, vertical: 2)`

<MaterialApp>
    <ThemeData for="theme" visualDensity="-1" />
    <Text for="home" data="Compact" />
</MaterialApp>

<MaterialApp>
    <ThemeData for="theme" visualDensity="-1,0" />
    <Text for="home" data="Compact horizontally" />
</MaterialApp>

WidgetStateProperty<T>

The default config can wrap these values with WidgetStateProperty.all(...):

Dart type	XML format
`WidgetStateProperty<Color>`	Same as `Color`.
`WidgetStateProperty<double>`	A numeric double value.
`WidgetStateProperty<EdgeInsetsGeometry>`	Same as `EdgeInsetsGeometry`.
`WidgetStateProperty<Size>`	Same as `Size`.

<ElevatedButton>
    <ButtonStyle for="style"
                 backgroundColor="#0066CC"
                 elevation="2"
                 padding="8,12,8,12"
                 fixedSize="120x40" />
    <Text for="child" data="Save" />
</ElevatedButton>

Custom Parsers

The formats above come from the default parser rules generated into each inflater's parseAttribute() method. Applications can add new rules or override existing ones in xwidget_config.yaml.

Parser lookup is ordered from most specific to most general:

ClassName:argumentName
*:argumentName
ArgumentType

Use a class-and-argument rule for one constructor argument, a wildcard argument rule for a common attribute name, or a type rule for every argument of that Dart type. The default config uses wildcard rules for *:width and *:height, so any attribute named width or height is parsed as a double before type-based rules are considered.

<SizedBox width="240" height="120" />

If no parser exists, the attribute value is passed through to the inflater as-is. For a literal XML value like name="settings", that value is a String. For a whole-attribute EL expression like value="${object}", the value can be any Dart object, including a function.

<ListTile>
    <Text for="title" data="Settings" />
</ListTile>

inflaters:
  constructor_arg_parsers:
    "MyWidget:customProp": "parseCustomProp(value)"
    "*:width": "parseDouble(value)"
    "Color": "parseColor(value)"

Custom parser functions must be available to the generated inflater file through inflaters.imports or an include file. In the config above, this XML calls parseCustomProp(value):

<MyWidget customProp="custom-format-value" />